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authorJeremy Fitzhardinge <jeremy@goop.org>2008-08-20 17:02:19 -0700
committerIngo Molnar <mingo@elte.hu>2008-08-21 13:52:58 +0200
commit994025caba3e6beade9bde84dd1b70d9d250f27b (patch)
tree0fe4d6f08d252af1db6a631182725085bb76442b /arch/x86/xen/spinlock.c
parent168d2f464ab9860f0d1e66cf1f9684973222f1c6 (diff)
xen: add debugfs support
Add support for exporting statistics on mmu updates, multicall batching and pv spinlocks into debugfs. The base path is xen/ and each subsystem adds its own directory: mmu, multicalls, spinlocks. In each directory, writing 1 to "zero_stats" will cause the corresponding stats to be zeroed the next time they're updated. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Acked-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/xen/spinlock.c')
-rw-r--r--arch/x86/xen/spinlock.c165
1 files changed, 162 insertions, 3 deletions
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 4884bc603aa..0d8f3b2d9be 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -4,6 +4,8 @@
*/
#include <linux/kernel_stat.h>
#include <linux/spinlock.h>
+#include <linux/debugfs.h>
+#include <linux/log2.h>
#include <asm/paravirt.h>
@@ -11,6 +13,93 @@
#include <xen/events.h>
#include "xen-ops.h"
+#include "debugfs.h"
+
+#ifdef CONFIG_XEN_DEBUG_FS
+static struct xen_spinlock_stats
+{
+ u64 taken;
+ u32 taken_slow;
+ u32 taken_slow_nested;
+ u32 taken_slow_pickup;
+ u32 taken_slow_spurious;
+
+ u64 released;
+ u32 released_slow;
+ u32 released_slow_kicked;
+
+#define HISTO_BUCKETS 20
+ u32 histo_spin_fast[HISTO_BUCKETS+1];
+ u32 histo_spin[HISTO_BUCKETS+1];
+
+ u64 spinning_time;
+ u64 total_time;
+} spinlock_stats;
+
+static u8 zero_stats;
+
+static unsigned lock_timeout = 1 << 10;
+#define TIMEOUT lock_timeout
+
+static inline void check_zero(void)
+{
+ if (unlikely(zero_stats)) {
+ memset(&spinlock_stats, 0, sizeof(spinlock_stats));
+ zero_stats = 0;
+ }
+}
+
+#define ADD_STATS(elem, val) \
+ do { check_zero(); spinlock_stats.elem += (val); } while(0)
+
+static inline u64 spin_time_start(void)
+{
+ return xen_clocksource_read();
+}
+
+static void __spin_time_accum(u64 delta, u32 *array)
+{
+ unsigned index = ilog2(delta);
+
+ check_zero();
+
+ if (index < HISTO_BUCKETS)
+ array[index]++;
+ else
+ array[HISTO_BUCKETS]++;
+}
+
+static inline void spin_time_accum_fast(u64 start)
+{
+ u32 delta = xen_clocksource_read() - start;
+
+ __spin_time_accum(delta, spinlock_stats.histo_spin_fast);
+ spinlock_stats.spinning_time += delta;
+}
+
+static inline void spin_time_accum(u64 start)
+{
+ u32 delta = xen_clocksource_read() - start;
+
+ __spin_time_accum(delta, spinlock_stats.histo_spin);
+ spinlock_stats.total_time += delta;
+}
+#else /* !CONFIG_XEN_DEBUG_FS */
+#define TIMEOUT (1 << 10)
+#define ADD_STATS(elem, val) do { (void)(val); } while(0)
+
+static inline u64 spin_time_start(void)
+{
+ return 0;
+}
+
+static inline void spin_time_accum_fast(u64 start)
+{
+}
+static inline void spin_time_accum(u64 start)
+{
+}
+#endif /* CONFIG_XEN_DEBUG_FS */
struct xen_spinlock {
unsigned char lock; /* 0 -> free; 1 -> locked */
@@ -92,6 +181,9 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock)
/* announce we're spinning */
prev = spinning_lock(xl);
+ ADD_STATS(taken_slow, 1);
+ ADD_STATS(taken_slow_nested, prev != NULL);
+
do {
/* clear pending */
xen_clear_irq_pending(irq);
@@ -100,6 +192,8 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock)
we weren't looking */
ret = xen_spin_trylock(lock);
if (ret) {
+ ADD_STATS(taken_slow_pickup, 1);
+
/*
* If we interrupted another spinlock while it
* was blocking, make sure it doesn't block
@@ -120,6 +214,7 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock)
* pending.
*/
xen_poll_irq(irq);
+ ADD_STATS(taken_slow_spurious, !xen_test_irq_pending(irq));
} while (!xen_test_irq_pending(irq)); /* check for spurious wakeups */
kstat_this_cpu.irqs[irq]++;
@@ -132,11 +227,18 @@ out:
static void xen_spin_lock(struct raw_spinlock *lock)
{
struct xen_spinlock *xl = (struct xen_spinlock *)lock;
- int timeout;
+ unsigned timeout;
u8 oldval;
+ u64 start_spin;
+
+ ADD_STATS(taken, 1);
+
+ start_spin = spin_time_start();
do {
- timeout = 1 << 10;
+ u64 start_spin_fast = spin_time_start();
+
+ timeout = TIMEOUT;
asm("1: xchgb %1,%0\n"
" testb %1,%1\n"
@@ -151,16 +253,22 @@ static void xen_spin_lock(struct raw_spinlock *lock)
: "1" (1)
: "memory");
- } while (unlikely(oldval != 0 && !xen_spin_lock_slow(lock)));
+ spin_time_accum_fast(start_spin_fast);
+ } while (unlikely(oldval != 0 && (TIMEOUT == ~0 || !xen_spin_lock_slow(lock))));
+
+ spin_time_accum(start_spin);
}
static noinline void xen_spin_unlock_slow(struct xen_spinlock *xl)
{
int cpu;
+ ADD_STATS(released_slow, 1);
+
for_each_online_cpu(cpu) {
/* XXX should mix up next cpu selection */
if (per_cpu(lock_spinners, cpu) == xl) {
+ ADD_STATS(released_slow_kicked, 1);
xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
break;
}
@@ -171,6 +279,8 @@ static void xen_spin_unlock(struct raw_spinlock *lock)
{
struct xen_spinlock *xl = (struct xen_spinlock *)lock;
+ ADD_STATS(released, 1);
+
smp_wmb(); /* make sure no writes get moved after unlock */
xl->lock = 0; /* release lock */
@@ -216,3 +326,52 @@ void __init xen_init_spinlocks(void)
pv_lock_ops.spin_trylock = xen_spin_trylock;
pv_lock_ops.spin_unlock = xen_spin_unlock;
}
+
+#ifdef CONFIG_XEN_DEBUG_FS
+
+static struct dentry *d_spin_debug;
+
+static int __init xen_spinlock_debugfs(void)
+{
+ struct dentry *d_xen = xen_init_debugfs();
+
+ if (d_xen == NULL)
+ return -ENOMEM;
+
+ d_spin_debug = debugfs_create_dir("spinlocks", d_xen);
+
+ debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats);
+
+ debugfs_create_u32("timeout", 0644, d_spin_debug, &lock_timeout);
+
+ debugfs_create_u64("taken", 0444, d_spin_debug, &spinlock_stats.taken);
+ debugfs_create_u32("taken_slow", 0444, d_spin_debug,
+ &spinlock_stats.taken_slow);
+ debugfs_create_u32("taken_slow_nested", 0444, d_spin_debug,
+ &spinlock_stats.taken_slow_nested);
+ debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug,
+ &spinlock_stats.taken_slow_pickup);
+ debugfs_create_u32("taken_slow_spurious", 0444, d_spin_debug,
+ &spinlock_stats.taken_slow_spurious);
+
+ debugfs_create_u64("released", 0444, d_spin_debug, &spinlock_stats.released);
+ debugfs_create_u32("released_slow", 0444, d_spin_debug,
+ &spinlock_stats.released_slow);
+ debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug,
+ &spinlock_stats.released_slow_kicked);
+
+ debugfs_create_u64("time_spinning", 0444, d_spin_debug,
+ &spinlock_stats.spinning_time);
+ debugfs_create_u64("time_total", 0444, d_spin_debug,
+ &spinlock_stats.total_time);
+
+ xen_debugfs_create_u32_array("histo_total", 0444, d_spin_debug,
+ spinlock_stats.histo_spin, HISTO_BUCKETS + 1);
+ xen_debugfs_create_u32_array("histo_spinning", 0444, d_spin_debug,
+ spinlock_stats.histo_spin_fast, HISTO_BUCKETS + 1);
+
+ return 0;
+}
+fs_initcall(xen_spinlock_debugfs);
+
+#endif /* CONFIG_XEN_DEBUG_FS */